The present disclosure relates to a hydrolysis-stable mesoporous silica material and to a method for producing the hydrolysis-stable mesoporous silica material. The present disclosure further relates to the use of the hydrolysis-stable mesoporous silica material as sensor material.
Surface-functionalized mesoporous silica materials can be used for sensor applications in water-containing gases. The pores of these functionalized materials have functional groups with the capacity to undergo basic reaction with water. As a result it is possible to determine, for example, the carbon dioxide content of the water-containing gas, by using electrodes mounted on the functionalized material to measure changes in the electrical properties of the material. This application requires the incorporation of liquid water into the pores by means of capillary condensation. With materials of these kinds, however, the risk exists of the Si—O—Si bonds, which produce the firm attachment to the pore surface of the organic functionalities that are needed for hydrophilization of the pore surface, undergoing hydrolysis and in this way the organic functionalities possibly become detached. A further risk lies in the hydrolyzability of the SiO2 pore structure, since many of these materials have very thin pore walls only a few SiO2 molecule layers thick.
For the purpose of improving the hydrolysis resistance of the silane framework, Wahab M. A. and Ciabin H. in “Hydrothermally stable periodic mesoporous ethane-silica and bimodal mesoporous nanostructures”, J. Nanosci. Nanotechnol. 2011, October; 11(10):8481-7, proposed joining two (—O)3Si units to one another via a short organic group. In this case, in addition to the aforementioned statistical effect, there is also an increase in the hydrophobicity of the framework. With measures of this kind it would be possible generally to achieve hydrolysis stability for such sensor materials. It is nevertheless necessary, moreover, to achieve the required chemical properties of the material, namely the hydrophilicity of its pore surface and the base functionality.